Research On Adsorption Property Of Heavy Metals Onto The Landfill Liners

There is some poisonous and harmful substance in the leachate of morden landfills,including heavy metals.It maybe pollute underground water and threaten health of human beings.In order to prevent underground water being polluted,there are usually composite liners in landfills.Adding materials capable of strongly adsorbing pollutants into liners,such as granular activated carbon and humus,can also effectively stop heavy metals ions from migrating.However,these materials are too expensive to be widely used in landfill liner.In this research,the clay and montmorillonite are used to make landfill liners.There are parts involved in this paper.In the first part of the paper,the batch experiment has been carried out to study the adsorption behavior of heavy metals ions on clay, montmorillonite and its modified derivative in aqueous medium.The effects of various factors, such as shaking time, frequence of shaking, initial concentration of heavy metals ions, pH value, tempreture, amount of clays on the adsorption capability have also been discussed. The results show that pseudo-second order kinetics model can describe the adsorption of heavy metals ions on clays very well.The process of adsorption is controlled by film diffusion and particle diffusion.It is an endothermic process accompaning the increase of disorder of the system and can be occured spontaneously.In the second part,there are mainly geological experiments.The optimal moisture content can be conformed from the experiments and the composite liners are made under this condition.After this,the hydraulic conductivity and unconfined compressive strength can be determined.The liner consists of two layers placed upon each other and each layer has a specific composition.The reactive agents present in top layer and bottom layer are transported to the interface of both layers to form a precipitate which in time will seal the pores on the interface after adding water in it.It is based on the formation of CaCO₃ and CaSiO₃ precipitate in the pores on the interface of the two layers adjacent.When it is broken,the agents can still react and form a membrane again.So,the composite liner has self-repairing properties.The concentrations of ions of the solution through the liners can be measured. So the diffusion mechanism of heavy metals ions in liners can be studied.